The present invention relates, in a process of manufacturing a semiconductor device or the like, to a substrate and a micro-structure, which have a reference scale utilized in a length measurement of a wiring pattern or the like, a method of making the reference scale, and a method of measuring a length of a wiring pattern in the micro-structure.
In recent years, a due to progress in micromachining techniques, micro-structures such as integrated circuits and semiconductor devices have been increasingly micronized, and wiring patterns or the like are provided with a spacing of only several μm, for instance. Since this dimension becomes a factor determining a basic performance of the micro-structure, such as frequency characteristic, of an electronic circuit, there is a demand for accurate measurement of a length of the micro-structure.
As a length measuring method, although various methods are provided, there is known a method of length-measuring from a beam scanning distance or a secondary electron image, in which a signal change (contrast change place) when scanning has been made a reference by a beam system of a scanning electron microscope (SEM) or the like. This length measuring method utilizing the SEM is adapted such that a micron bar becoming the reference of the length is displayed generally on a monitor confirming an FIB image of a length measuring object article. By comparing this micro bar with the length measuring object article, there have been measured the length of the length measuring object article, a spacing between the length measuring object articles adjoining each other, and the like (for example, refer to JP-A-2001-357812 Gazette).
Incidentally, in an observation by an optical microscope, there is adopted a method utilizing a scale having been displayed in a lens, not the micro bar. Further, in an observation field, in compliance with a measurement object article, there is required the micro bar of an optimum size in a range of nm-mm.
However, in the above conventional method, the following problems have been identified.
That is, since the micron bar is one displayed two-dimensionally on an image plane, it is possible to accurately length-measure the measurement object article by utilizing the micro bar in a case where an FIB is irradiated perpendicularly to the measurement object article, but it has been impossible to perform an accurate length measurement in a case where the measurement object article is slanted. In other words, since it follows that the length measuring object article slanting with respect to an irradiating direction of the FIB is length-measured, it is impossible to simply compare the length measuring object article with the micron bar, so that it has been impossible to perform the length measurement with the micro bar being made the reference.
Further, in a case where the optical microscope has been utilized, since even the micro bar does not exist, the length measurement has been difficult to obtain.
The present invention is one made in view of such circumstances, and its object is to provide a substrate and a micro structure, in which the length measurement can be accurately and easily performed irrespective of a posture of the length measuring object article, a method of making the reference scale, and a method of measuring the length of the micro structure.